Influence of essential amino acid balancing post-partum on lactation performance by dairy cows through a meta-analysis

Abstract Text: A meta-analysis was performed to evaluate the impact of dietary individual essential amino acids (AA) concentration (g of AA/Mcal of ME) on lactation performance by dairy cows during the initial 4 weeks of lactation. The dataset was comprised of 20 unpublished feeding trials evaluating the effect of lysine or lysine/methionine supplementation. Diets were formulated with CPM/CNCPS which provided a complete dietary AA profile. Data were analyzed using Proc Mixed of SAS with treatments as Fixed effects and trial as a Random effect. Positive relationships between methionine and milk and milk protein yields were observed (P < 0.10 and P < 0.07, respectively) during weeks 1 to 4. Actual- and energy-corrected milk (ECM) yields increased (P < 0.04 and P < 0.08, respectively) along with lysine concentration on weeks 1, 2 and 4 whereas milk protein yield increased (P < 0.03) during the 4 initial weeks of lactation. Arginine and threonine were negatively related to milk fat content and yield (P < 0.07 and P < 0.10, respectively) on weeks 3 and 4. Quadratic relationships between milk or milk protein yields and dietary concentrations of leucine and phenylalanine (P < 0.06 and P < 0.09, respectively) were observed during weeks 1 to 4. Isoleucine concentration was negatively related to ECM and milk protein yields (P < 0.09 and P < 0.07, respectively) during weeks 3 and 4 and to milk and milk fat yields (P < 0.09 and P < 0.05, respectively) on week 3.  Dietary valine was related positively to ECM (P < 0.10) and negatively to milk protein concentration (P < 0.08) on weeks 2 and 3.  On weeks 3 and 4, a positive relationship between milk yield and valine was observed (P < 0.08). Dietary histidine was related positively to milk yield (P < 0.07) but negatively to milk protein content (P < 0.06) on weeks 2 to 4.  Concentration of tryptophan was negatively related to ECM (P < 0.07), milk fat content (P < 0.03) and yield (P < 0.02). Overall, benefits on lactation performance were observed with increased concentrations of methionine, lysine, valine and histidine. In contrast, isoleucine and tryptophan were negatively related to lactation performance whereas arginine and threonine depressed milk fat. These results underscore the importance of amino acid balancing beyond lysine: methionine ratio when formulating diets for early lactation dairy cows.

Keywords: amino acids, post-partum, lactation performance